1. Field of the Invention
The invention relates to a nail driving gun, more particularly to a barrel unit with a removable cover plate for a nail driving gun.
2. Description of the Related Art
In a known nail driving gun, a nail feeding unit aligns a nail from a nail cartridge with a nail impelling unit so as to discharge the nail via a barrel unit. Jamming of the nail driving gun usually occurs, thereby preventing the discharge of the nail through the barrel unit. In order to resume proper operation of the nail driving gun, a cover plate of the barrel unit is removed to remedy the cause of jamming. Thus, it is important for the barrel unit to have a structure which facilitates installation and removal of the cover plate.
Referring to FIGS. 1 and 2, a conventional barrel unit is shown to be installed on a front end of a nail driving gun 10 and includes an elongated base plate 11 which extends forwardly from the housing of the nail driving gun 10. The base plate 11 has a top side formed with a longitudinal discharge groove 110 and a pair of upwardly extending hooking lugs 12 which are disposed respectively on opposite sides of the discharge groove 110 and which are integral with the base plate 11. The cover plate 13 is to be superimposed on the base plate 11 and is formed with a pair of slots 14 which permit extension of the hooking lugs 12 therethrough. An operating lever 15 is mounted pivotally on the cover plate 13. A U-shaped fastener 16 has two ends connected pivotally to the operating lever 15. After the fastener 16 has been pivoted relative to the operating lever 15 so as to engage the hooking lugs 12, the operating lever 15 is pivoted rearwardly so as to pull the fastener 16 to engage tightly the hooking lugs 12 and so as to press the cover plate 13 against the base plate 11. When it is desired to remove the cover plate 13, the operating lever 15 is pivoted forwardly to permit removal of the fastener 16 from the hooking lugs 12 and to permit lifting of the cover plate 13 from the base plate 11.
As shown in FIG. 3, the shock experienced by the nail driving gun during a nail driving operation may cause slight movement of the cover plate 13 relative to the base plate 11 which, in turn, may loosen engagement between the fastener 16 and the hooking lugs 12. Thus, untimely removal of the cover plate 13 from the base plate 11 is likely to occur when the aforementioned conventional barrel unit is in use.
Referring to FIG. 4, another conventional barrel unit is shown to be similarly installed on a front end of a nail driving gun 20 and includes an elongated base plate 21 which extends forwardly from the housing of the nail driving gun 20. The base plate 21 has a top side formed with a longitudinal discharge groove 210 and a pair of upwardly extending hooking lugs 22 which are disposed respectively on opposite sides of the discharge groove 210 and which are integral with the base plate 21. The cover plate 23 has one end mounted pivotally on the base plate 21 by means of a pin (not shown) and is to be superimposed on the base plate 21. An operating lever 24 is mounted pivotally on the cover plate 23. A U-shaped fastener 25 has two ends connected pivotally to the operating lever 24. When the cover plate 23 is superimposed on the base plate 21, the fastener 25 can be pivoted relative to the operating lever 24 so as to engage the hooking lugs 22. At this time, the operating lever 24 can be pivoted rearwardly so as to pull the fastener 25 to engage tightly the hooking lugs 22. When it is desired to access the discharge groove 210, the operating lever 24 is pivoted forwardly to permit removal of the fastener 25 from the hooking lugs 22 and to permit pivoting movement of the cover plate 23 relative to the base plate 21 for accessing the discharge groove 210.
If the nail driving gun 20 is used to drive several nails in rapid succession, the shock experienced by the cover plate 23 during the nail driving operation may loosen the pin from the base plate 21, thereby resulting in untimely removal of the cover plate 23 from the base plate 21.